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Title: Identifying the Active Surfaces of Electrochemically Tuned LiCoO 2 for Oxygen Evolution Reaction

Abstract

Identification of active sites for catalytic processes has both fundamental and technological implications for rational design of future catalysts. Herein, we study the active surfaces of layered lithium cobalt oxide (LCO) for the oxygen evolution reaction (OER) using the enhancement effect of electrochemical delithiation (De-LCO). Our theoretical results indicate that the most stable (0001) surface has a very large overpotential for OER independent of lithium content. In contrast, edge sites such as the nonpolar (1120) and polar (0112) surfaces are predicted to be highly active and dependent on (de)lithiation. The effect of lithium extraction from LCO on the surfaces and their OER activities can be understood by the increase of Co 4+ sites relative to Co 3+ and by the shift of active oxygen 2p states. Experimentally, it is demonstrated that LCO nanosheets, which dominantly expose the (0001) surface show negligible OER enhancement upon delithiation. However, a noticeable increase in OER activity (~0.1 V in overpotential shift at 10 mA cm –2) is observed for the LCO nanoparticles, where the basal plane is greatly diminished to expose the edge sites, consistent with the theoretical simulations. In addition, we find that the OER activity of De-LCO nanosheets can be improved ifmore » we adopt an acid etching method on LCO to create more active edge sites, which in turn provides a strong evidence for the theoretical indication.« less

Authors:
ORCiD logo [1];  [1];  [1];  [2];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1];  [3];  [3]
  1. Stanford Univ., Stanford, CA (United States)
  2. Harvard Univ., Cambridge, MA (United States)
  3. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1368758
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 17; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Lu, Zhiyi, Chen, Guangxu, Li, Yanbin, Wang, Haotian, Xie, Jin, Liao, Lei, Liu, Chong, Liu, Yayuan, Wu, Tong, Li, Yuzhang, Luntz, Alan C., Bajdich, Michal, and Cui, Yi. Identifying the Active Surfaces of Electrochemically Tuned LiCoO2 for Oxygen Evolution Reaction. United States: N. p., 2017. Web. doi:10.1021/jacs.7b02622.
Lu, Zhiyi, Chen, Guangxu, Li, Yanbin, Wang, Haotian, Xie, Jin, Liao, Lei, Liu, Chong, Liu, Yayuan, Wu, Tong, Li, Yuzhang, Luntz, Alan C., Bajdich, Michal, & Cui, Yi. Identifying the Active Surfaces of Electrochemically Tuned LiCoO2 for Oxygen Evolution Reaction. United States. doi:10.1021/jacs.7b02622.
Lu, Zhiyi, Chen, Guangxu, Li, Yanbin, Wang, Haotian, Xie, Jin, Liao, Lei, Liu, Chong, Liu, Yayuan, Wu, Tong, Li, Yuzhang, Luntz, Alan C., Bajdich, Michal, and Cui, Yi. Tue . "Identifying the Active Surfaces of Electrochemically Tuned LiCoO2 for Oxygen Evolution Reaction". United States. doi:10.1021/jacs.7b02622. https://www.osti.gov/servlets/purl/1368758.
@article{osti_1368758,
title = {Identifying the Active Surfaces of Electrochemically Tuned LiCoO2 for Oxygen Evolution Reaction},
author = {Lu, Zhiyi and Chen, Guangxu and Li, Yanbin and Wang, Haotian and Xie, Jin and Liao, Lei and Liu, Chong and Liu, Yayuan and Wu, Tong and Li, Yuzhang and Luntz, Alan C. and Bajdich, Michal and Cui, Yi},
abstractNote = {Identification of active sites for catalytic processes has both fundamental and technological implications for rational design of future catalysts. Herein, we study the active surfaces of layered lithium cobalt oxide (LCO) for the oxygen evolution reaction (OER) using the enhancement effect of electrochemical delithiation (De-LCO). Our theoretical results indicate that the most stable (0001) surface has a very large overpotential for OER independent of lithium content. In contrast, edge sites such as the nonpolar (1120) and polar (0112) surfaces are predicted to be highly active and dependent on (de)lithiation. The effect of lithium extraction from LCO on the surfaces and their OER activities can be understood by the increase of Co4+ sites relative to Co3+ and by the shift of active oxygen 2p states. Experimentally, it is demonstrated that LCO nanosheets, which dominantly expose the (0001) surface show negligible OER enhancement upon delithiation. However, a noticeable increase in OER activity (~0.1 V in overpotential shift at 10 mA cm–2) is observed for the LCO nanoparticles, where the basal plane is greatly diminished to expose the edge sites, consistent with the theoretical simulations. In addition, we find that the OER activity of De-LCO nanosheets can be improved if we adopt an acid etching method on LCO to create more active edge sites, which in turn provides a strong evidence for the theoretical indication.},
doi = {10.1021/jacs.7b02622},
journal = {Journal of the American Chemical Society},
number = 17,
volume = 139,
place = {United States},
year = {Tue Apr 18 00:00:00 EDT 2017},
month = {Tue Apr 18 00:00:00 EDT 2017}
}

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Cited by: 6works
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  • The layered LiMO{sub 2} (M = Co, Ni) compounds, which are of potential interest for Li-ion batteries, were synthesized at low temperatures by treatment under hydrothermal conditions of LiOH{center_dot}H{sub 2}O aqueous solutions containing powdered H{sub x}MO{sub 2} phases. The authors studied the reaction mechanism and the influence of temperature, pressure, water dilution, and precursor ratio on the degree of progress of the ion exchange process. Single-phase LiMO{sub 2} can be obtained in 48 h at 160 C under an air pressure of 60 bars from an MOOH/LiOH{center_dot}H{sub 2}O/H{sub 2}O mixture. The degree of advancement of the exchange reaction for Mmore » = Co was monitored in situ using an autoclave which allows the withdrawal of samples in the course of the reaction. From transmission electron microscopy coupled with x-ray diffraction studies the authors conclude that the reaction occurs by surface H{sup +}/Li{sup +} exchange and is accompanied by a progressive breaking of the particles due to an interfacial collapse phenomenon. Infrared studies indicate that the LiCoO{sub 2} and LiNiO{sub 2} phases obtained are contaminated by carbonates that can more easily be eliminated in the case of LiCoO{sub 2} by water washing and post-heating treatments under primary vacuum at 200 C for 2 days. Once the ion-exchange parameters are controlled, the LiMO{sub 2} products exhibit electrochemical performances comparable to those of high-temperature made phases.« less
  • While the surface atomic structure of RuO 2 has been well studied in ultra high vacuum, much less is known about the interaction between water and RuO 2 in aqueous solution. In this work, in situ surface X-ray scattering measurements combined with density functional theory (DFT) were used to determine the surface structural changes on single-crystal RuO2(110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogen electrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of –H 2O on the coordinatively unsaturated Ru sites (CUS)more » and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant to the oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by a neighboring –OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with their energetics from DFT led to a new OER pathway, where the deprotonation of the –OH group used to stabilize –OO was found to be rate-limiting.« less
    Cited by 1
  • Surface structural transitions and active sites are identified using X-ray scattering and density functional theory.
  • Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of LiCoO 2 nanorods with sizes in the range from 9 to 40 nm were studied in alkaline solution. The sides of these nanorods were terminated with low-index surfaces such as (003) while the tips were terminated largely with high-index surfaces such as (104) as revealed by high-resolution transmission electron microscopy. Electron energy loss spectroscopy demonstrated that low-spin Co 3+ prevailed on the sides, while the tips exhibited predominantly high- or intermediate-spin Co 3+. We correlated the electronic and atomic structure to higher specific ORR and OER activities at themore » tips as compared to the sides, which was accompanied by more facile redox of Co 2+/3+ and higher charge transferred per unit area. These findings highlight the critical role of surface terminations and electronic structures of transition metal oxides on the ORR and OER activity.« less
  • We studied oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of LiCoO 2 nanorods with sizes in the range from 9 to 40 nm in alkaline solution. We also terminated the sides of these nanorods with low-index surfaces such as (003), while the tips were terminated largely with high-index surfaces such as (104), as revealed by high-resolution transmission electron microscopy. Electron energy loss spectroscopy demonstrated that low-spin Co 3+ prevailed on the sides, while the tips exhibited predominantly high- or intermediate-spin Co 3+. Finally, we correlated the electronic and atomic structure to higher specific ORR and OER activitiesmore » at the tips as compared to the sides, which was accompanied by more facile redox of Co 2+/3+ and higher charge transferred per unit area. These findings highlight the critical role of surface terminations and electronic structures of transition-metal oxides on the ORR and OER activity.« less